1. Field of the Invention
The invention relates to a process for the preparation of endo-nortropine using 8-benzyl-nortropan-3-one perchlorate as the intermediate, as well as the latter salt.
2. Description of the Related Art
The prior art discloses numerous processes for the preparation of endo-nortropine and the latter substance itself. Endo-nortropine is the key product for the production of important azoniaspironortropanol esters, which are used as pharmaceuticals, particularly spasmolytics (cf. particularly German patent 1 194 422), whereas 8-benzyl-nortropan-3-one perchlorate is not known.
Hitherto only the picrate, hydrochloride and hydrobromide of 8-benzyl-nortropan-3-one are known, but for which no further use possibilities exist. 8-benzyl-nortropan-3-one is also mentioned in EP-A1-42 705 as an intermediate in the production of azabicycloalkane derivatives, whose pharmacological activity is described.
In principle, there are three known process procedures for the preparation of endo-nortropine, namely the saponification of tropane alkaloids, such as nor-1-hyoscyamine, convolvine and convolamine. However, the saponification of three alkaloids is not profitable, because the starting products are rare and expensive. Thus, as is known tropine is oxidatively demethylated in order to prepare endo-nortropine. In addition, photochemical methods for the demethylation and demethylation with ethyl chloroformates are known, cf. e.g. DE-A1-35 46 218. However, it is a disadvantage of said dealkylation process that expensive and in part environmentally prejudicial chemicals have to be used as starting products, which in turn can only be produced with difficulty. The known processes mainly also operate with overpressure and are usually not stereoselective.